Motivation and Approach

Reliable message routing in MANETs is challenging not only because the network topology is constantly changing, but also because nodes must use a broadcast medium to probe the topology and send data. The result is that much bandwidth is wasted due to flooding of topology discovery messages and the resulting collisions due to radio interference from simultaneous message transmissions. This problem is significantly worse in VANETs, where vehicles tend to travel at high speed in large groups, often separated by signal-weakening obstructions such as buildings.

Virtual Ferry Networking (VFN) is a mobility-assisted approach for enabling distributed systems in these challenging conditions. Specifically, VFN relies on the aggregated movements of independent vehicles to provide self-configuring virtual paths over which to ferry messages. By using multiple vehicles to ferry messages, VFN provides higher reliability and more flexibility than a single ferry vehicle or fixed ferry path. Any vehicle traveling along part of this path can become a ferry for messages during that period.

A VFN system consists of one or more sets of road segments over which vehicles follow an aggressive protocol aimed at improving network reliability, efficiency and connectivity. Each set of road segments defines a circuit that we refer to as a virtual ferrying route. All vehicles that are driving on (or near) a portion of a VFR are said to be participating in the VFN. The figure below presents a simple VFN with a single VFR in a city grid (downtown Chicago). The participating vehicles (dark triangles) use message aggregation, awareness of other vehicles' paths, and adaptive message transmission rates to optimize communication by leveraging store-and-forward style communication.

Figure 1: A simple VFN topology in downtown Chicago. The thicker, lighter shaded roads represent the virtual path over which messages are ferried, and the vehicles with dark borders are participating in the VFN.